Receiving sheet for use as a master or copy in the dtr process



Oct. 3, 1967 R. E. ORMSBEE 3, I

RECEIVING SHEET FOR USE AS A MASTER OR COPY IN THE DTR PROCESS FiledSept. 20, 1965 FIG. 3

IN VEN TOR Bath 1?. Ormsbee.

WMYM azzys United States Patent 3,344,741 RECEIVING SHEET FOR USE AS AMASTER 0R CQPY IN THE DTR PROCESS Ruth E. Ormshee, River Forest, 111.,assignor to A. B. Dick Company, Niles, 111., a corporation of IllinoisFiled Sept. 20, 1965, Ser. No. 488,479 4 Claims. (Cl. 101462) Thisinvention relates to the production of copy by the diffusion transferreversal process, generally referred to as the DTR process, and itrelates more particularly to the preparation of an image receiving sheetwhich can be used both as a sheet for the production of single copies oras a master from which multiple copies can be produced by lithographicduplication. More specifically, the invention relates to a lithographicmaster which can be imaged by the DTR process and which can also be usedas a single copy sheet.

Copy sheets for use in the production of single copy by the DTR processhave been avilable for some time; however, such sheets cannot generallybe employed as lithographic masters from which multiple copies of goodquality can be produced when imaged by DTR technique.

The difiiculty in the fabrication of a lithographic master for imagingby diffusion transfer resides in the formulation of a sheet whichembodies the characteristics essential for lithographic reproduction,including (1) a sheet having high wet strength and dimensional stabilityto enable repeated wetting with aqueous repellent and oleophilic inkcomposition in the production of inked copies therefrom, (2) whichembodies a water insoluble, water receptive, ink repellent surfaceessential to the imaged master, and (*3) which has surfacecharacteristics that provide the critical balance between waterreceptivity in the non-imaged portions and ink receptivity in the imagedportions whereby the aqueous repellent with which the sheet is first wetwill preferentially be received by the non-imaged hydrophilic portionsof the imaged master while the precipitated silver image deposited onthe surface diffusion transfer from an exposed negative will repel theaqueous repellent and be preferentially wet by the oleophilic inkcomposition in inking the master for use in the production of copy.

To the present, it has only been possible to make use of a DTRlithographic plate formed of an aluminum base sheet having a surfacetreated to render the surface hydrophilic and lithographic as byreaction with a water soluble silicate, acrylic acid, or by anodizationto form an oxide layer and in which the lithographic surface is providedwith a nucleating agent, such as colloidal silver, silver sulfide,cadmium sufide and the like for nucleating the conversion of the solublesilver halide complex difiused from the unexposed portions of thenegative to precipitate silver as an ink receptive, water repellentimage on the lithographic surface of the aluminum sheet.

Such aluminum lithographic plates are, of course, expensive andunsuitable for use as single copy whereby the plate is limited toapplications where an extremely large number of copies are to beproduced.

DTR plates for lithographic duplication have been formed of coated paperbase sheets wherein the paper base sheet is formulated to contain aresinous binder to impart wet strength and which is overcoated with agelatin coating containing the nucleating agent. Such Wet strengthpapers are non-lithographic such that the procedure required forpreparation of the plate for lithographic duplication has includedtreatment of the surface of the plate, after the plate has been imaged,with an acid etch composition for conversion of the non-imaged portionof the plate to a hydrophilic, ink repellent, lithographic surface. Suchmultiple steps for the preparation of an imaged master for lithographicduplication is objectionable, at least from the standpoint of time,labor and materials, and even then a satisfactory plate for theproduction of a large number of copies of good quality is difficult toachieve.

Further, the nucleating agent is incorporated in a gelatin coatingapplied to the surface of a paper base sheet. Gelatin coatings of thetype described are diflicult to apply and they also provide a surfacewhich presents problems during image development by diffusion transferin that the gelatin coating is adhesive and makes separation of thenegative and positive sheets more difiicult and it also retards dryingand introduces curl into the master thereby to militate against theproduction of an imaged plate which lies flat on the plate cylinder ofthe duplicating machine.

It is an object of this invention to produce and to provide a method forproducing a coated paper lithographic plate adapted for imaging from anexposed negative in a DTR process; which can be used interchangeably asa direct single copy or which can be used as an imaged lithographicmaster from which multiple inked copies can be produced by lithographicduplication; which does not require a pre-etch or etch applied after animage has been formed on the plate for rendering the non-imaged portionshydrophilic and lithographic; which provides the desired criticalbalance between the ink receptivity of the imaged portion formed on theplate and the water receptivity of the non-imaged portion; which doesnot require the used of a gelatin top coat for support of nucleatingagent; which dries rapidly upon separation from the exposed negative toproduce a fiat, flexible, imaged master which can be mounted on theplate cylinder of a lithographic press; and from which a large number ofcopies of good quality can be produced.

These and other objects and advantages of this invention willhereinafter appear and for purposes of illustration, but not oflimitation, an embodiment of the invention is shown in the accompanyingdrawing, in which FIG. 1 is a perspective view partially in section of areceiving sheet embodying the features of this invention;

FIG. 2 is a sectional elevational View of the arrangement of elementsfor imaging the receiving sheet by an exposed negative; and

FIG. 3 is a perspective view partially in section similar to that ofFIG. 1 showing the imaged receiving sheet.

The concepts of this invention will hereinafter be described byreferenoe to a specific example for the preparation of a coated paperreceiving sheet or master and the method for use of same in thepreparation of an imaged lithographic plate from which multiple copiescan be produced or which can be used as a single copy.

Polyvinylidene chloride latex (60% solids- Serfene H30Morton ChemicalCo.) ml 1.5

Acrylic emulsion polymer (46% solids-Rhoplex AC33-Rohm & Hass Co.) g .25

Saponin (10% solution) ml .01

The coating composition is applied by roller coating, flow coating orother suitable paper coating process in coating weights of 0.5 to 10.0pounds per 3000 square feet of surface area, or to a water resistantpaper base sheet 10 such as Schoeller water resistant base, or Barytapaper and the like. The coating 12 is air dried or preferably forcedried in an air drying oven at a temperature within the range of ISO-300F.

After sheeting and punching to provide the openings 14 in the leadingedge of the sheet for mounting as a lithographic plate onto a platecylinder of a lithographic press, the coated paper is ready for use as areceiving sheet.

Example 2 subject matter to be reproduced, the exposed negative isbrought into surface contact with the coated side of the receiving sheetafter the exposed negative or both the negative and the receiving sheethave been wet with a conventional developing solution, as represented bythe following developing composition, which is diluted in the ratio of 1to 1 with tap water before use.

Example 3 Developer composition:

H O ml 800 Phenidone g 3.0 Sodium sulfite g 163.0 Hydroquinone g 30.0Sodium hydroxide g 30.0 Sodium thiosulfate-penta g 20.0 Potassiumbromide g 3.0 H to volume quart 1 In response to wetting with thedeveloping solution, the exposed portion 26 of the silver halide coatingis reduced to silver while the silver halide in the relatively unexposedportion 28 is converted into a soluble silver halide complex whichdissolves in the solution for transfer by diffusion from the exposednegative to the coated surface of the receiving sheet.

The nucleating agent present in the surface of the receiving sheetoperates to reduce the silver halide complex to colloidal particles ofsilver or other reduction reaction product which becomes strongly bondedto the coated surface of the sheet and defines an oleophilic, inkreceptive, water repellent image 30 on an otherwise ink repellent, waterreceptive hydrophilic, water insoluble, lithographic surface.

The receiving sheet is then separated from the negative sheet.Separation is easy by reason of the absence of gelatin in the coating 12on the receiving sheet and also by reason of the presence of colloidalsilica as an essential and major component of said coating. Theseparated receiving sheet also appears immediately to dry possiblybecause of the presence in the coating of colloidal silica. In anyevent, the imaged sheet can be used directly as a single copy or it. canbe immediately, or after a period of time, mounted on the plate cylinderof a lithographic press for use in the production of a number of inkedcopies by conventional lithographic duplicating technique. However, itis preferred to fix the image and condition the plate by treatment ofthe imaged surface with a conditioner represented by the following:

Example 4 Conditioner:

H O ml 69.5 Carboxymethylhydroxyethyl cellulose-43 low (Hercules PowderC-o.) g 0.2 Sodium nitrate g 2.0 Ammonium phosphate g 1.0

Glycerine g 19.0 Ethyl alcohol g 7.0 Cetylpryridinium bromide g 0.05

The conditioner is wiped onto the surface of the image receiving sheet,before or after mounting on the press,

and then inked copies are produced by first wetting the surface withaqueous repellent to wet out the unsilvered, non-imaged portions 32 ofthe plate and then wetting with an oleaginous ink composition which isnot received by the wet non-imaged portions but is received by the unwetoleophilic portions 30 for transfer of the ink image from the sheet tocopy paper in a direct lithographic process or to a blanket in an offsetprocess of lithographic duplication.

It will be understood that the formulation of the devel-' oping solutionand the conditioner is not critical to the invention in thatconventional photographic developers and lithographic conditioners canbe employed.

An important concept-of this invention resides in the non-gelatincoating applied to the paper base sheet for use in the preparation ofthe receiving sheet. It is not essential for the polyvinylidene chlorideand the acrylic emulsion polymer to be present in the coatingcomposition or for both to be present together in combination with thecolloidal silica since either one or the other can be employed or thecolloidal silica can be employed alone, as illustrated by the followingexamples:

Example 5 Water 30 Colloidal silica (30% SiO -Ludox LSDu Pont) 30 Sodiumsulfide (0.5% solution) 2 Silver nitrate (0.5% solution) 3Polyvinylidene chloride latex (60% solids) 4 Saponin (10% solution) 4.

Example 6 Water l5 Colloidal silica (30% SiO Ludox l-lS-Du Pont) 30Sodium sulfide (0.5 solution) 2 Silver nitrate (0.5% solution) 3 Acrylicemulsion polymer (46% solids) .5 'Saponin (10% solution) .1

Example 7 G. Colloidal silica (Ludox LSDu Pont) Silver sulfide (34%solution) 25 Silver nitrate (68% solution) 25 The amount and type ofnucleating agent can be varied depending upon the formulation of thedeveloper and the composition of the silver halide negative although anyconventional nucleating agents can be employed. In the use of sodiumsulfide and silver nitrate, in the preferred practice of this invention,it is preferred to make use of the materials in the ratio of about 1part by weight of sodium sulfide to 11.5 parts by weight of silvernitrate although it is permissible to make use of the materials withinthe range which comprises 1 part by weight of the sodium sulfide to 02parts by weight of silver nitrate.

When used, the amount of resinous solids in the coating composition,when based upon the SiO content of colloidal silica, can range from 9parts by weight of Si0 to .255.0 parts by weight of the combinedresinous polymers and 9 parts by Weight of SiO to .14 parts by weight ofthe resinous material when formed of acrylic emulsion polymer, or 9parts by weight of SiO to 0.5-5.0 parts by weight of resinous binderwhen formed of polyvinylidene chloride, all on a solids basis. Theamount of nucleating agent can be varied over .a fairly wide rangedepending upon the agent employed but it is preferred to make use of anamount Within the range of .1-.5 part by Weight nucleating agent per 9,parts by weight of SiO The saponin is a surface active agent derivedfrom plant glucosides such as tn'terpenoid saponin but the surfaceactive agent is not essential to the formulation of the coatingcomposition since it serves primarily for the stabilization thereof andother surface active agents can be used.

It will be apparent from the foregoing that I have pro vided a new andimproved receiving sheet for imaging by diffusion transfer reversaltechnique and in which the receiving sheet may be used as a singledirect copy or as a lithographic master from which multiple copies ofgood quality can be produced.

It will be understood that changes may be made in the details ofconstruction, formulation and operation without departing from thespirit of the invention, especially as defined in the following claims.

I claim:

1. A receiving sheet for imaging by a dilfusion transfer reversalprocess comprising a paper base sheet and a coating on the surface ofthe paper base sheet consisting essentially of the combination ofcolloidal silica, a nucleating agent for reduction of a soluble silverhalide complex to an oleophilic ink receptive imaging material andpresent in an amount within the range of 0.1 to 0.5 part by weight per 9parts by weight of colloidal silica and in which the nucleating agentcomprises the combination of sodium sulfide and silver nitrate presentin the ratio of 1 part by weight of sodium sulfide to 1 to 1.5 parts byweight of silver nitrate, and a resinous binder selected from the groupconsisting of a vinylidene chloride polymer and an acrylate polymer andin which the coating is a water insoluble coating which is waterreceptive, ink repellent, hydrophilic and lithographic.

2. A receiving sheet as claimed in claim 1 in which the vinylidenechloride polymer is present in the coating in an amount within the rangeof 0.5 to 5.0 parts by weight to 9 parts by weight of colloidal silicacalculated as SiO 3. A lithographic imaged master as claimed in claim 1in which the resinous binder is an acrylate emulsion polymer present inan amount within the range of 0.1 to 4 parts by weight per 9 parts byweight of colloidal silica.

4. A receiving sheet for imaging by diffusion transfer reversal processcomprising a paper base sheet and a coating on the surface of the paperbase sheet consisting essentially of the combination of colloidal silicaand a nucleating agent for reduction of soluble silver halide complex toan oleophilic ink receptive imaging material in which the nucleatingagent is present in an amount within the range of 0.1 to 0.5 part byWeight per 9 parts by weight of colloidal silica and in which thenucleating agent comprises the combination of sodium sulfide and silvernitrate present in the ratio of 1 part by weight of sodium sulfide to 1to 1.5 parts 'by weight of silver nitrate and in which the coating iswater insoluble, water receptive, ink repellent, hydrophilic andlithographic.

References Cited UNITED STATES PATENTS 2,698,237 12/1954 Land 96293,062,648 11/ 1962 Crawford 9633 3,157,117 11/1964 Relph et a1. 101149.23,161,508 12/1964 Hepher et al. 9633 3,220,837 11/1965 Land et al. 96333,247,793 4/1966 Beatty et al l01--149.2

ROBERT E. PULFREY, Primary Examiner.

I. A. BELL, Assistant Examiner.

1. A RECEIVING SHEET FOR IMAGING BY A DIFFUSION TRANSFER REVERSALPROCESS COMPRISING A PAPER BASE SHEET AND A COATING ON THE SURFACE OFTHE PAPER BASE SHEET CONSISTING ESSENTIALLY OF THE COMBINATION OFCOLLOIDAL SILICA, A NUCLEATING AGENT FOR REDUCTION OF A SOLUBLE SILVERHALIDE COMPLEX TO AN OLEOPHILIC INK RECEPTIVE IMAGING MATERIAL ANDPRESENT IN AN AMOUNT WITHIN THE RANGE OF 0.1 TO 0.5 PART BY WEIGHT PER 9PARTS BY WEIGHT OF COLLOIDAL SILICA AND IN WHICH THE NUCLEATING AGENTCOMPRISES THE COMBINATION OF SODIUM SULFIDE AND SILVER NITRATE PRESENTIN THE RATIO OF 1 PART BY WEIGHT OF SODIUM SULFIDE TO 1 TO 1.5 PARTS BYWEIGHT OF SILVER NITRATE, AND A RESINOUS BINDERR SELECTED FROM THE GROUPCONSISTING OF A VINYLIDENE CHLOFIDE POLYMER AND AN ACRYLATE POLYMER ANDIN WHICH THE COATING IS A WATER INSOLUBLE COATING WHICH IS WATERRECEPTIVE, INK REPELLENT, HYDROPHILIC AND LITHOGRAPHIC.